1. Field of the Invention
The present invention relates to an image pick-up device, and more particularly to an image pick-up device for outputting a picked-up image as digital image data.
2. Related Background Art
It has been widely conducted to utilize an output image from an image pick-up device in other device as image data. For example, image data is outputted to an image printer for print-out or the image data is read into a personal computer and combined with characters and graphs to prepare a report and it is further printed out by a color printer.
Two major systems for the configuration of such a system have been known.
In the first system, a conventional analog video signal is generated in the image pick-up device and it is outputted to an extension board expanded in a personal computer or an image printer, analog-digital converted by an AD converter, the digital video signal is stored in a field memory or a frame memory, and the stored image data is outputted to the personal computer or the image printer through an interface circuit.
In the second system, a digital video signal is generated in the image-pick-up device and it is stored in a field memory or a frame memory provided in the image pick-up device and the stored image data is outputted to the external personal computer or image printer through the interface circuit provided in the image pick-up device.
However, the prior art device has the following problems.
First, the biggest problem is the number of pixels of the image pickup device. The above device mostly uses image pick-up elements in accordance with a standard television system. The number of pixels of the image pick-up device is in the order of 500.times.500 for a popular type and in the order of 800.times.600 for a high number of pixels type. When it is to be printed by a 300 dpi printer, an image size is only approximately 40 to 60 mm and when a larger size is to be printed, a resolution of the image is reduced which results in a coarse image.
A special purpose image pick-up device uses more pixels, in the order of 1000.times.1000 but even with such a device, the printed image size is only approximately 80 mm square. Since the area of such image pick-up device is very large, a manufacturing yield is very low. Further, since a driving frequency is very high such as 30 to 40 MHz, a cost of the device is very high and it is not practical for common use. An image size which is practically required is in the order of 200.times.150 mm and the prior art device cannot attain such an image size.
Another problem is an image quality. In the first system of the prior art device, since the analog video signal is first generated and then it is converted to the digital image data, a color band is narrow because of a limitation by the specification of the standard television system. As a result, the colors spread when the image is displayed on a display device of the personal computer or printed by the printer. In the second system, the image is distorted in a periphery by the aberration of an image pick-up lens or the colors spread, which result in the degradation of the image quality.